1. Field of the Invention
The present invention relates to an ink cartridge, and more particularly, to an ink cartridge for an image forming apparatus wherein a cartridge body and a lid are more precisely welded to each other to avoid ink blending in the cartridge, assure generation and maintenance of a proper negative pressure inside the cartridge, and reduce manufacturing defects.
2. Description of the Related Art
In general, an ink cartridge, capable of supplying ink upon printing, is employed for an inkjet printer and the like. A conventional ink cartridge is mainly divided into a cartridge body, holding ink and provided with ink filters and ink heads, and a lid. The cartridge body and the lid have welding parts for welding the parts together.
FIG. 1 and FIG. 2 are a cross-sectional view and a plan view showing a conventional cartridge body 102 capable of holding three color inks, respectively. The cartridge body 102, as can be seen in FIGS. 1 and 2, includes foam chambers 106, ink chambers 108, first to third partitions 110, 112, and 113 partitioning respective color inks as well as the foam chambers 106, the ink chambers 108, ink filters 115, and ink heads 117.
The foam chambers 106 have foams 107 therein, and the foams 107 create a negative pressure inside the foam chambers 106. The ink filters 115 are mounted underneath the foam chambers 106, and remove foreign materials or contaminants that may be contained in ink. The paths through which respective color ink flows are formed under the ink filters 115, and on the ends mounted the ink heads 117. The ink heads 117 eject proper amounts of ink when printing so that printing can be done.
Ink is kept in the ink chambers 108 that are partitioned from the foam chambers 106 by the first partition 110. Further, the ink chambers 108 connect with the foam chambers 106 by way of link openings 111 formed at the bottom of the first partition 110.
Such ink chambers 108 and foam chambers 106, as shown in FIG. 2, are partitioned from each other for respective color inks. Separate ink filters 115 and ink heads 117 under the foam chambers 106 are used for respective color inks.
The cartridge body 102 structured as above is bonded to a lid 104 shown in FIG. 3 and FIG. 4 to seal the foam chambers 106 and the ink chambers 108 for the respective color inks. For the cartridge body 102 shown in FIG. 1 and FIG. 2, the first welding part 122 (shown in FIG. 1) formed on the top rim surface of the cartridge body 102 and the second welding part 124 (shown in FIG. 1) formed on the top surfaces of the first to third partitions are ultrasonically welded with the third welding part 126 and, the fourth welding part 128 which are formed on the lid 104.
FIG. 3 is a bottom view of the lid 104 covering the upper side of the cartridge body 102 having ink injection holes 119 and 120 through which ink can be injected into respective chambers. The third welding part 126 welded with the first welding part 122 (shown in FIG. 1) is shown as a one-dot chain line, and the third welding part 128 welded with the second welding part 124 is shown as a two-dot chain line. FIG. 4 is a view for showing the upper side of the lid 104, wherein it can be seen that the ink injection holes 119 and 120 are formed for the foam chambers 106 and ink chambers 108 respectively for respective color inks.
In general, when an ink cartridge is manufactured, the lid 104 is placed on the upper side of the cartridge body 102, the horn of an ultrasonic welder (not shown) is closely contacted on, and pressed, against the lid 104, and vertically vibrates at a frequency of about 20 KHz in a certain amplitude. With such vibration, high heat is generated on the friction surfaces, that is, the first to fourth welding parts 122, 124, 126, and 128 between the cartridge body 102 and the lid 104, so that the first welding part 122 is welded with the third welding part 126, and the second welding part 124 is welded with the fourth part 128.
The first welding part 122, as shown in enlarged views of FIG. 1 and FIG. 3, has a triangular shape tilted to one side, and contacts the third welding part 126 which has a flat surface. Further, the second welding part 124 has a triangular shape, and is welded with the fourth welding part 128 which has a flat surface.
Accordingly, when sealing the conventional ink cartridge by ultrasonic welding, the cartridge body 102 and the lid 104 may slide against each other due to the vibration since the ultrasonic welder (not shown) generates vibration while pressed to the lid 104 placed on the cartridge body 102.
Further, since the first to third partitions 110, 112, and 113, partitioning the chambers of the cartridge body 102, are relatively thin in thickness in relation to their length, the first to third partitions 110, 112, and 113 may move to the left and right due to instant pressure and vibration generated when the ultrasonic welder is pressed against them. Vibration energy is likely to be scattered, rather than being concentrated on the welding portions, due to bends of the partitions 110, 112, and 113. With such phenomena, the first to fourth welding parts 122, 124, 126, and 128 may partially have portions not melted, which leads to imperfect sealing.
In general, in operation of an ink cartridge, ink is injected into respective chambers through the ink injection holes 119 and 120, and ink injection holes 120, for ink injection into the ink chambers 108. are sealed during use. Ink is used through the ink heads 117 during printing, and, when the level of ink is lowered, ink, kept in the ink chamber 108, is supplied to the foam chamber 106 through the link opening 111 formed at the bottom of the first partition 110, so a negative pressure of the ink chamber 108 increases.
If the level of ink in the foam chamber 106 is gradually lowered, air externally flows into the foam chamber 106 through the ink injection holes 119 due to the negative pressure of the ink chamber 108. The airflow in forms air bubbles (not shown), and the air bubbles flow into the ink chamber 108 through the link opening 111. With such series of operations continuously repeated, the ink of the ink chamber 108 is consumed so that all the ink can be used up to the last ink remaining in the foam chamber 106.
In order to ideally use ink as above, it is essential to generate a proper negative pressure in the ink chamber 108. To generate the proper negative pressure, secure sealing, between exterior and interior air, has to be maintained by the sealing between the first welding part 122 and the third welding part 126 and between the second welding part 124 and the fourth welding part 128.
However, since the conventional ink cartridge has the first and second welding parts. 122 and 124 of the cartridge body 102 formed in a triangular shape, and also has the third and fourth welding parts 126 and 128 of the lid 104 formed in a flat shape, the parts slide against each other and vibration energy transfers are not sufficient between the parts during the ultrasonic welding. Due to such phenomena, welding is only partially carried out so that sealing between the cartridge body 102 and the lid 104 is not implemented preventing a negative pressure from being generated in the ink chamber 108 and causing a phenomenon of ink flowing down out of the ink head 117 due to gravity.
Further, in a case of non-welded portions on the second and fourth welding parts 124 and 128, respective color inks are blended together that should be separated by the second partition 112 and the third partition 113, to further degrade printing quality.